The invention relates to a roller for a fibre processing machine, for example a spinning preparation machine such as a flat card, cleaner or the like, flock feeder, roller card, nonwoven-forming machine or the like, having a wall of fibre-reinforced plastics material.
The effective spacing of the tips of a clothing from a machine element located opposite the clothing is called a carding nip. The said machine element can also have a clothing but could, instead, be formed by an encasing segment having a guide surface. The carding nip is decisive for the carding quality. The size (width) of the carding nip is a fundamental machine parameter, which influences both the technology (the fibre processing) and also the running characteristics of the machine. The carding nip is set as narrow as is possible (it is measured in tenths of a millimetre) without running the risk of a “collision” between the work elements. In order to ensure that the fibres are processed evenly, the nip must be as uniform as possible over the entire working width of the machine.
The carding nip is especially influenced, on the one hand, by the machine settings and, on the other hand, by the condition of the clothing. The most important carding nip in a carding machine having a revolving card top is located in the main carding zone, that is to say between the cylinder and the revolving card top unit. At least one of the clothings bounding the work spacing is in motion, usually both. In order to increase the production of the carding machine, endeavours are made to make the speed of rotation or velocity of the moving elements, in use, as high as fibre processing technology will allow. The work spacing changes as a function of the operational conditions, the change occurring in the radial direction (starting from the axis of rotation) of the cylinder.
In carding, larger amounts of fibre material are increasingly being processed per unit time, which results in higher speeds for the work elements and higher installed capacities. Increasing fibre material throughflow (production) leads to increased generation of heat as a result of the mechanical work, even when the work surface remains constant. At the same time, however, the technological result of carding (web uniformity, degree of cleaning, reduction of neps etc.) is being continually improved, leading to more work surfaces in carding engagement and to closer settings of those work surfaces with respect to the cylinder (drum). The proportion of synthetic fibres being processed is continually increasing, with more heat, compared with cotton, being produced as a result of friction from contact with the work surfaces of the machine. The work elements of high-performance carding machines today are fully enclosed on all sides in order to meet the high safety standards, to prevent emission of particles into the spinning room environment and to minimise the maintenance requirement of the machines. Gratings or even open material-guiding surfaces, which allow an exchange of air, belong to the past. As a result of the circumstances mentioned, there is a marked increase in the input of heat into the machine whereas there is a marked decrease in the heat removed by means of convection. The resulting increase in the heating of high-performance carding machines results in greater thermoelastic deformations, which, because of the unequal temperature field distribution, influence the set spacings of the work surfaces: the spacings between the cylinder and the card top, doffer, fixed card tops and separating-off locations decrease. In extreme cases, the nip set between the work surfaces can be completely used up as a result of thermal expansion so that components in relative motion collide, causing major damage to the high-performance carding machine concerned. Additionally, it is especially possible for the generation of heat in the work region of the carding machine to result in different thermal expansions when the temperature differences between the components are too large.
In a known roller of fibre-reinforced plastics material for a carding machine (EP 0 894 876 A), the reinforcing fibres are present in the form of an arrangement extending at least in part in the circumferential direction. The roller has a cylinder wall and cylinder ends made of fibre-reinforced plastics material. In order to achieve adequate stability, the roller must have a wall thickness (cylinder wall) of at least 10 mm—preferably at least 15 mm—that is uniform over its length. A winding method is employed, wherein fibres soaked with resin are wound around a shaping core which is removed from the end product. A disadvantage is the high cost both for manufacture and also for the fibre-reinforced plastics material for the thick cylinder wall. The cost for manufacture of the cylinder ends is also considerable. In addition, it is disadvantageous that, in the case of high-speed rollers for fibre-processing machines provided with clothings, the loading circumstances and operating conditions are difficult to master (constant carding nip) so that no rollers made from fibre-reinforced plastics material have been used hitherto for fibre-processing machines provided with clothings. A further disadvantage is that fibre-reinforced plastics material is poorly suited for the cylinder ends and the entire internal and hub regions.
It is an aim of the invention to provide an apparatus of the kind mentioned at the beginning that avoids or mitigates the mentioned disadvantages and that especially makes possible, by simple means, economical manufacture and adequate dimensional stability in use, namely a substantially constant carding nip.